Apparatus for determining the relative porosity of various porous materials



2,355,858 OROSITY Aug. 15, 1944. s H. HAHN ETAL APPARATUS FOR DETERMINING THE RELATIVE P OF VARIOUS POROUS MATERIALS Filed 0ct. 17, 1941 2 Sheets-Sheet 1,-

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Fig. is a aleng E il 6} M View @12 the 3191 M; the ms 1 6O w mm m i c by constant speed motor IS. The motor is and lamp 39 are wired in parallel and the switch 40 is wired in series with the lamp and motor. The apparatus is provided with a male electrical receptacle 4! into which may be inserted a female plug 42 carrying wires 43 to an electrical outlet which is the source of electrical energy to operate the apparatus. The wiring diagram within the porosity testing apparatus is quite simple with the switch 40 in series in the line and the lamp 39 and motor i9 in parallel.

To operate the porosity testing apparatus [3 in connection with a piece of latex rubber sponge 12 the foraminous pedestal i is placed on a flat surface 44, the rubber sponge is placed on the pedestal, and the porosity meter is lifted by means of the handle 45 and placed on the sponge. The control switch 40 is turned on and this im mediately starts the constant speed motor I! and lights up the lamp 39. The motor l9 operates the rotary fan ll to draw air from the vacuum chamber [4 and set up a flow of air through the sponge i2. As there is resistance to this flow of air there will alway be a partial vacuum in the vacuum chamber 14 while the apparatus is in operation. In this way porosity may be measured as the degree of porosity isan inverse function of the amount of vacuum maintained in the vacuum chamber I 4. An orifice i6 is placed between the fan I! and the chamber l4 so that there is increased resistance to the flow of air. The increased resistance to flow provided by the orifice I6 i directly proportional to the square of the air flow so that instead of a non-linear function-in the fan characteristics we now get a more nearly linear function. This means that the vacuum in the vacuum chamber [4 is consequently a more nearly linear function of the air flow through the porous materials being tested and that the vacuum as indicated by the indicator arm 33 on the linear scale 36 is correspondingly a true indication of the porosity of the material being tested. In other words, when testing two materials, one of which is twice as porous as the other, the less porous one will cause the arm 33 to move a certain distance while the more porous one will cause the arm to move substantially twice as far. As can be seen, the orifice diameter used depends upon the fan characteristics of draft versus flow which is in turn controlled by the size and speed of the fan. In the present case the motor is a 3 H. P. capacitor type motor, the fan is a No. 00 Torrington Manufa turing Company fan of 3" x 1 /2" size with 27 forward curving blades and operating at 3600 R. P. M., and the orifice is -74; inch in diameter. The orifice may be placed as indicated at IE, or anywhere in the enclosed air stream as, for instance, at 2!. The air from the fan is exhausted through a circular opening 2! in the fan housing I8 and discharged through a square opening 23 provided in the sheet metal cover plate 24, the

opening 23 being covered by a piece of wire screen 25. As a practical matter the opening 23 in the cover plate 24 is spaced 9. short distance from the opening 2 l in the fan housing l8 so that if the first opening 23 is. accidently closed the free flow of expelled air will not be impeded but will flow through other vents in the cover plate 24. To measure the degree of vacuum in the'vacuum chamber l4 and thus the porosity of the material being tested a dry vacuum gauge 26 is connected to the vacuum chamber H by means of a rightangled coupling 21. In the apparatus as illustrated in Fig. 1 the vacuum causes the movable diaphragm 28 to move to the right thereby moving the indicator arm 33 to the left side of the scale 36 which is the low porosity side. If the material being tested is highly porous the vacuum will be very slight and the indicator arm will arrange itself, by means of the pull of the spring lever 30, on the right side of the scale. Because of the construction of the draft gauge and the manner in which the indicator point 33 is connected to it, the pointer would ordinarily remain on the right side of the graduated scale 38 when the apparatus is turned off by means of the switch 40. As this is the high porosity side of the scale, such action might be confusing to anyone not familiar with the construction of the apparatus. To prevent such confusion, an attachment is provided on the switch 40 (Fig. 4) so that when the switch is turned to the left to turn it off, a hinged coupling arm 46 moves out and forces the indicator pointer 33 to the left where it is rigidly held in the zero position. This also protects the indicating means from damage due to jar when the portable apparatus is being moved about. When the switch 40 is turned to the right again in a short are to turn the apparatus on, the pressure on the indicator is removed so that it is free to act in conjunction with the diaphragm of the pressure gauge 26. This locking of the pointer on the off position has, of course, no effect on the efficient operation of the apparatus when the switch is turned on and the pressure on the indicator is removed.

. The apparatus described herein may be used to test the porosity of a wide variety of porous materials. The scale used to show this porosity may be graduated in absolute units or it may have no units at all and be used to show the relativ porosity of two or more pieces of porous material or materials. As can be seen the apparatus has the potentialities of a wide range of possible uses. Because of its ready portability, it is especially valuable as a sales demonstration device for use in showing the relative porosities of competitive materials.

Having disclosed our invention herein it is our object to protect it broadly within the spirit and scope of the appended claims.

We claim:

1. Porosity measuring apparatus comprising, in combination, power driven means for setting up and maintaining a current of fluid through the porous material being tested, indicating means responsive to such flow of fluid, manually operated means for starting and stopping the said power driven means, and means actuated by the last said manually operated means for setting the indicator means to a pre-determined position when the apparatus is stopped.

2. An apparatus for measuring the porosity of porous materials comprising a foraminous platform designed to permit the free flow of air through the surface of the platform, the porous material that is to be tested resting on the platform, and porosity measuring apparatus in contact with the porous material and comprising, in combination, power driven means forsett-ing up and maintaining a current of air through the porous material, indicating means responsive to such flow of air, manually operated means for starting and stopping the said power driven means; and means actuated by the last said manually operated means for setting the indicator means to a pre-determined position when the measuring apparatus is stopped.

3. An apparatus for measuring the porosity of porous materials comprising a foraminous plat form designed to permit the free iiow of air through the surface of the platform, the porous material to be tested resting on the platform, and. porosity measuring apparatus in contact with the porous material and comprising, in combination, a vacuum chamber in contact with the porous material, a fan for evacuating air from said vacuum chamber, a substantially constant speed motor for driving said fan, an outlet port for expelling the air, indicating means for measuring the vacuum created by said evacuation, manually operated means for starting and stopping said fan, and means actuated by the last said manually operated means for setting the indicator means to a rare-determined position when the apparatus is stopped.

4 in an apparatus for measuring the porosity of porous materials an indicator means for indi eating the degree of porosity, a switch for starting and stopping the apparatus, and means actu atecl by said switch for setting the indicator rhea s to a pre-cletermined position when the ap paratus is stopped.

5. in an apparatus for measuring the porosity oi porous materials an indicator means for in shooting degree of porosity, a scale against which the indicating means operates, a switch for start ing and stopping the apparatus, and means actuatecl by said switch for setting the indicator means to the zero position on the low porosity side of the scale.

8. in an apparatus for measuring the porosity of porous materials, indicator means for indi eating the degree of porosity, operatoncontrollea means for starting and stopping functioning of the apparatus, and meansaotuatetl by saiol oper ator-=-contro1led means for resetting the izrriicator means to a pro-determined position.

*2". Porosity measuring apparatus of the type in which a current of air or the like is maint necl flowing through a sample of material undergoing" test and a fluid-flow characteristic of the cur rent is measured as an indication of porosity, said apparatus consisting essentially of two con selbcontained units both light in Weight ior ready transportaloility; one of said units comnria ing a platform-like member adapted to be placer-i on. table or the like and having a ioraminous surface supported so as'to permit tree flow of air under and upward through the foraminous stir the upper side of the said unit being orally fiat tor receiving and supporting a epic of material to be tested; the other solo. units comprising a substantially enclosed structure hav ing a generally flat bottom for resting on sairl sample of material to be tested, saitl structure having an air tnlet opening ...-1 saicl bottom an aiz' outlet opening having free access to the atmosphere, said second unit also including means substantially entirely enclosed. by the saitl second unit structure for drawing air in through t e sample and. through the saidv air-lnlet o riving air out the said, a outlet with similarly enclos current of air while t second. unit, the inslicat lole externally oi the unit; an tus being so constructed Etiflfl may Ice conducted by merely unit a sample oi porous mat rial placing the second unit thereover s on. the sample, and starting the Cllil. o=

duping means.

partition having an. orifice therein 8. Porosity measuring apparatus of the type in which a current of air or the like is maintained flowing through a sample of material undergoing test and a fluid-flow characteristic of the current is measured as an indication of porosity, said, ap-= paratus consisting essentially of two compact, self-contained, and. independent units both light in Weight for ready transportaliility; one of said. units comprising a platform-lii-te member adapt ed to be placed on a table or the like having a foraminous surface supported so as to perrnit free new of air under and upward through the ioraminous surface, the upper side said unit being generally flat for receiving supporting a sample of material to be tested; the other of said units comprising a an. s enclosecl box=liite structure prov" tile means for ready manual po; ing generally flat bottom for resting or sample of material to he tested, said 5 having an air-inlet opening in sairi oo' atmosphere, said second unit also means substantially entirely v said sample and through t and for driving air out the air-outlet op gether with similarly enclosed means urine; and indicating the rate oi flow oi while it is passing through saici second i. indicative of the porosity of being tested, saicl indicating be conducted. by merely placing on th a sample of porous material to "so test the second unit thereover so that it rests a" sample, and starting the air current pro means.

9. Porosity indicating con'it. container having a wall portion. aelaptetl to he placed against a surface of porous material said wall providing a charnher adjacent aperture in communication therewi second. chamber adjacent said. partition; sa e tition having an orifice therein providing c munication between two said chambers; second chamber havin a second, openii municatlng with the outside atmosphere another wall portion or" saicl container; fan k in the second chamber for causin our of air to flow through the apparatus re= sponsive to flow of through the appars r indicating a porosity characteristic of the in J? rialtestecl. i

iii. Porosit inchcating apparatus comprisi a placed. against a suriace of porous he tested, Wall portion ha c an ape. therein the portions of the wall aperture losing adapted to forin seal with. porous material; partition tor ling 9. Vi,

amber extending into the cor a; erture; sairl aperture opening chamber; outlet means incl. e commimieating with the outside atrnoe another wall portion said cont communication between. the vacuum chamber outlet means; means within the container ior creating vacuum in said vacuum chamber thereby causing a current of air to flow through the material being tested, thence through the apparatus and out through the said outlet means; and means responsive to flow of air through the apparatus for indicating a porosity characteristic of the material being tested.

11. Porosity indicating apparatus comprising a readily-portable, unitary device including a platelike wall structure adapted to be placed upon a surface of porous material to be tested and to form a seal therewith; said plate-like wall structure having an aperture therein for permitting flow of air through the apparatus and the material being tested; air-conducting means leading from said aperture to a second aperture communicating with the atmosphere; a partition having an orifice therein interposed in said air-conducing means between the two said apex-tines; means disposed above and in substantial alignment with the first said aperture for causing a current of air to how through the said airconducting means and the material being tested; and means responsive to flow of air through the apparatus for indicating a porosity characteristic of the material being tested; said air-conducting means, said partition, said air-flow producing means and said indicating means all being supported by the said plate-like wall structure and being readily portable therewith as a unit.

- STUART H. HAHN.

ROBERT H. JUDSON. 

